Have you ever wondered what different effects or stomp boxes are supposed to do? Well, wonder no more. Here's a run down on what the most widely used ones do.
Compressor - The gain of the amplifier is varied to reduce the dynamic range of the signal.
Tremolo - Tremolo produces a periodic variation in the amplitude (volume) of the note. A sine wave applied as input to a voltage-controlled amplifier produces this effect.
Overdrive and Distortion - The signal is cranked up past the limits of the amplifier, resulting in clipping. Example: Guitar on Spirit in the Sky by Norman Greenbaum.
Wah-Wah - An effect that gives the guitar an almost vocal effect. Example: "White Room" by Cream, used by Eric Clapton. Primarily invented for the Organ Music, but then somehow found by Jimi Hendrix and Eric Clapton and used for their personal gain.
Ring Modulation"Organic" effect - Makes weird noises.
Equalizer - Adjusts the frequency response in a number of different bands of EQ. Variants include the Parametric EQ, which instead of flatly boosting and cutting frequencies, curves the frequency response to include changes in adjacent frequencies. Examples: Boss PN-2 and GE-2
Clean Boost or any other "booster" - Takes your guitar signal, kicks it up a notch, and then sends it on its merry way. Generally used for preventing signal loss through long chains of effects units (pedals) and getting overdrive tones out of a tube amp. On stage, used for volume boosts for solos. Examples: Zachary Vex's Super Hard On, catalinbread's Super Chile Picoso.
Heil Talk Box - A vowel-tuned wah that actually takes your voice as the wah control.
Delay - First used by Les Paul, e.g. I'm Forever Blowing Bubbles. (Modern digital delay units, the first of which was the Eventide Harmonizer, involve sound waves being converted from analog to digital signals, and clocked through large banks of RAM memory. Paul achieved time delay by stretching audiotape between two reel-to-reel tape decks spaced several feet apart.)
Echo - Uses delays to simulate an echo
Chorus - Usually short delays to simulate more than one person playing at a time
Flanging - Uses very short variable delays to cause a changing comb filter effect
Reverb - Simulates echoes in stadiums, halls, other performance areas. Even actual surfaces, such as plate metal and metal springs, are sometimes simulated.
Pitch Shifter - Also introduced by the Harmonizer, which has a knob on the front to "change your pitch up." First used on Itchycoo Park by Small Faces.
Vibrato - Vibrato refers to a variation in frequency of a note, for example as an opera singer holding one note for a long time will vary the frequency up and down. A sine wave applied as input to a voltage-controlled oscillator produces this effect.Guitarists often use the terms "vibrato" and "tremolo" inconsistently. A so-called vibrato unit in a guitar amplifier actually produces tremolo, while a tremolo arm on a guitar produces vibrato. However, finger vibrato is genuine vibrato.
Other specific effects
Defretter - It simulates a fretless guitar
Acoustic Guitar Simulator - Simulates an acoustic guitar. Example: Boss AC-2
Rotary SpeakerA Leslie speaker simulation effect. One particular effect of this type was made famous by Jimi Hendrix.
Pickup Simulation - Simulates either a single coil pickup if the musician has a humbucker orr vice-versa.
Ambience Modeling - Creates an ambience through some amalgam of effects.
Cabinet Modeling - Models your tone to act like its coming out of a set of old greenbacks in a vintage AC30 cabinet, or most other examples you can think of.
Guitar amplifier Modeling - Models your tone to sound like its going through a 5150 or some other ridiculously expensive amplifier.
These types of effects are usually digital, and can therefore be found as features of effect processors such as the Boss ME series and Vox multieffects.